Objectives: To analyze the genotypes and the resistance mechanisms in a multidrug-resistant K. pneumoniae outbreak in our hospital.

Methods: Antimicrobial susceptibility was tested by microdilution and disk diffusion method. The b-lactamase family was screened by PCR. Sequencing of PCR products was performed in selected isolates. Integrons were analyzed by the Levesque method. The molecular characterization of isolates was performed by pulsed field gel electrophoresis (PFGE, XbaI) and by Multi Locus Sequence Typing (MLST). The quinolone-resistant determinant regions (QRDRs) of gyrA and parC were sequenced.

Results: From August 2007 until June 2009, 107 multidrug resistant K. pneumoniae isolates were detected from clinical samples of 44 patients, 73% of them admitted to the ICU. The source of isolates was: urine (n = 28), blood (n = 20), bronchial aspirate (n = 20), catheter (n = 13), abdominal samples (n = 12), wound swabs (n = 6), bronchoalveolar lavage (n = 5) and other (n = 3). The strains were resistant to amoxicillin/clavulanic acid, piperacillin/tazobactam, tobramycin, amikacin and ciprofloxacin and had diminished susceptibility to cefepime (MICs range 14mg/ml). This multidrug-resistant pattern was transferred by conjugation to E. coli J532. A common PFGE pattern was observed in all K. pneumoniae isolates related to ST14 (16-11-11-1) by MLST. K. pneumoniae isolates and their transconjugants had the blaOXA gene, confirmed as blaOXA-1 after sequencing. The blaOXA-1 gene was located in the variable region of a class I integron which also contains the aac(6')Ib-cr gene. The sequencing of the QRDRs revealed a S83F change in GyrA and no changes in ParC.

Conclusion: The increase in multidrug-resistant K. pneumoniae isolates in our hospital was associated to the clonal spread of an epidemic strain belonging to ST14 and harboring blaOXA-1 and aac(6')Ib-cr genes in a class I integron. Control measures and continuous surveillance are needed in order to prevent the spread of these epidemic strains.

Session Details

Date:

10/04/2010

Time:

00:00-00:00

Session name:

Abstracts 20th European Congress of Clinical Microbiology and Infectious Diseases